Solar Cells

Abstract

A photovoltaic cell comprising a semiconductor wafer comprising a front, light receiving surface and an opposite back surface, a passivation layer on at least the back surface, a doped layer opposite in conductivity type to the wafer over the passivation layer, an induced inversion layer, a dielectric layer over the doped layer, and one or more localized emitter contacts and one or more localized base contacts on at least the back surface extending at least through the dielectric layer; and a neutral surface photovoltaic cell comprising a semiconductor wafer comprising a front, light receiving surface and an opposite back surface, neutral passivation layer on at least the back surface, a dielectric layer over the passivation layer, and one or more localized emitter contacts and one or more localized base contacts on at least the back surface extending at least through the dielectric layer.

1 . A photovoltaic cell comprising a semiconductor wafer comprising a front, light receiving surface and an opposite back surface, a passivation layer on at least the back surface, a doped layer opposite in conductivity type to the wafer over the passivation layer, an induced inversion layer, a dielectric layer over the doped layer, and one or more localized emitter contacts and one or more localized base contacts on at least the back surface extending at least through the dielectric layer. 
   
   
       2 . The photovoltaic cell of  claim 1  wherein the one or more localized emitter contacts and the one or more localized base contacts are all on the back side of the photovoltaic cell. 
   
   
       3 . The photovoltaic cell of  claim 1  wherein the one or more localized emitter contacts and the one or more localized base contact are laser fired contacts. 
   
   
       4 . The photovoltaic cell of  claim 1  wherein at least a portion of the base contacts comprise an insulation layer electrically isolating the base contact from the inversion layer. 
   
   
       5 . The photovoltaic cell of  claim 1  wherein the semiconductor wafer comprises p-type silicon. 
   
   
       6 . The photovoltaic cell of  claim 1  wherein the semiconductor wafer comprises n-type silicon. 
   
   
       7 . The photovoltaic cell of  claim 1  wherein at least a portion of the localized base contacts extend through the dielectric layer, the doped layer and the passivation layer. 
   
   
       8 . A photovoltaic cell comprising a semiconductor wafer comprising a front, light receiving surface and an opposite back surface, a passivation layer on at least the back surface, a doped layer opposite in conductivity type to the wafer over the passivation layer, a dielectric layer over the doped layer, and one or more localized emitter contacts and one or more localized base contacts on at least the back surface extending at least through the dielectric layer. 
   
   
       9 . A neutral surface photovoltaic cell comprising a semiconductor wafer comprising a front, light receiving surface and an opposite back surface, a neutral passivation layer on at least the back surface, a dielectric layer over the passivation layer, and one or more localized emitter contacts and one or more localized base contacts on at least the back surface extending at least through the dielectric layer. 
   
   
       10 . The photovoltaic cell of  claim 9  wherein the localized emitter contact and localized base contacts are all on the back surface of the photovoltaic cell. 
   
   
       11 . The photovoltaic cell of  claim 9  wherein the wherein the one or more localized emitter contacts and one or more localized base contacts are laser fired contacts. 
   
   
       12 . The photovoltaic cell of  claim 9  wherein the neutral passivation layer is a-Si:H and is up to about 100 nm thick. 
   
   
       13 . The photovoltaic cell of  claim 12  wherein the a-Si:H is at least about 40 nm thick. 
   
   
       14 . A method for manufacturing a photovoltaic cell comprising a semiconductor wafer comprising silicon, a front surface and a back surface, the method comprising:
 a) depositing a passivation layer on the front and back surfaces of the wafer:   b) depositing a doped layer opposite in conductivity type to the wafer on at least the back surface of the wafer and over the passivation layer;   c) depositing a dielectric layer over at least the doped layer; and   d) forming localized base and emitter contacts on at least the back surface of the wafer and extending at least through the dielectric layer.   
   
   
       15 . The method of  claim 14  wherein the base contacts further comprise a layer of insulating material around at least a portion of the base contact. 
   
   
       16 . The method of  claim 14  wherein the photovoltaic cell comprises an induced inversion layer and the insulating material electrically insulates the base contact from the inversion layer. 
   
   
       17 . The method of  claim 14  wherein the localized base contacts and the localized emitter contacts are formed on the back surface of the photovoltaic cell in an interdigitated finger pattern. 
   
   
       18 . The method of  claim 14  wherein a first pattern of electrically conducting material is deposited on the back surface of the electrically connecting the base contacts, and a second pattern of electrically conducting material is deposited on the back surface electrically connecting the emitter contacts. 
   
   
       19 . The method of  claim 14  wherein the base and emitter contacts are laser fired contacts. 
   
   
       20 . A method for manufacturing a photovoltaic cell comprising a semiconductor wafer comprising silicon, a front surface and a back surface, the method comprising:
 a) depositing a passivation layer on at least the back surface of the wafer;   b) depositing a dielectric layer on at least the back surface of the wafer and over the passivation layer; and   c) forming localized base and emitter contacts on at least the back surface of the wafer extending at least through the dielectric layer.   
   
   
       21 . The method of  claim 20  wherein the dielectric layer is on the front and the back surface of the wafer. 
   
   
       22 . The method of  claim 20  wherein the passivation layer comprises a-Si:H and is about  4  to about  100  nm thick. 
   
   
       23 . The method of  claim 20  wherein the passivation layer and the dielectric layer is combined as one layer that is at least about 40 nm thick. 
   
   
       24 . The method of  claim 20  wherein the passivation layer and dielectric layer comprise a-Si:H. 
   
   
       25 . The method of  claim 20  wherein a thin doped layer is deposited over the passivation layer and is between the passivation layer and the dielectric layer. 
   
   
       26 . The method of  claim 25  wherein the thin doped layer comprises doped a-Si:H and is about 4 to about 20 nm thick.